1. Field of the Invention
The present invention relates to a technique for improving the image shake correction performance of an imaging apparatus.
2. Description of the Related Art
In imaging apparatuses, there has been a demand for advanced image shake correction functions for moving images. For example, there has been a demand for advanced functions for detecting and correcting image shake caused by hand vibration or the like in the in-plane rotational direction and rolling shutter distortion accompanied therewith. In interchangeable lens-type imaging apparatuses, there has been proposed a method for performing electronic image shake correction within a camera body for a captured image in conjunction with an optical image shake correction mechanism provided within an independently operating lens. Accumulated shake caused by shake or motion of an image in the vertical direction and the horizontal direction, which is the main element of the high-frequency components of hand vibration, is suppressed by optical image shake correction. On the other hand, the low-frequency components of shake of large amplitude and shake in the in-plane rotational direction, which cannot be suppressed by optical image shake correction, are suppressed by geometric deformation by electronic image shake correction.
Japanese Patent Laid-Open No. 2007-215114 discloses a technique for suppressing rolling shutter distortion, which is caused by employing a CMOS sensor and cannot be completely suppressed by optical image shake correction, by geometric deformation by electronic image shake correction. In addition, Japanese Patent No. 4178481 discloses a technique for suppressing the motion of an image other than shake of an image in the vertical direction and the horizontal direction which cannot be suppressed by optical image shake correction, i.e., the motion of an image in the in-plane rotational direction, by geometric deformation by electronic image shake correction.
In recent years, there has been a demand for a technique for dealing with not only shake caused by hand vibration but also shake caused by so-called “shooting while walking” by expanding an angle range in which image shake can be corrected mainly at the wide-angle end side. Japanese Patent No. 4692620 discloses a technique for removing the range limit of centering on optical image shake correction or the range limit of margin pixels for image shake correction on electronic image shake correction by intentionally releasing the low-frequency components of shake and not completely stopping the motion of an object image.
On the other hand, in imaging apparatuses having the integral functions of still image shooting and moving image shooting, an image shake correction system (hybrid image shake correction) that combines optical image shake correction and electronic image shake correction is employed. A hybrid image shake correction mechanism is expanding its loading area from the moving image shooting function of the conventional camera dedicated for moving image shooting to the moving image shooting function of an interchangeable lens-type imaging apparatus mainly used for still image shooting. With the aid of the moving image shooting function which can withstand the full-fledged shooting in an imaging apparatus, there has been a demand for achieving the advanced image shake correction function while maintaining the characteristic of the image shake correction function or the like upon shooting while walking.
When performing the hybrid image shake correction that combines optical image shake correction and electronic image shake correction, it is important for electronic image shake correction to obtain operation information about optical image shake correction so as to grasp what type of image shake correction has been carried out by optical image shake correction in terms of functional improvement. However, in the case of an interchangeable lens-type imaging apparatus, if an attempt is made to process operation information about an independently operating optical image shake correction mechanism provided within a lens barrel by transferring the operation information to the imaging apparatus main body, a significant system change is required. The conventional lens group is not designed to meet such a specification. Thus, in the communication mode between the camera and the lens, content information sufficient for image shake correction may not be transferred from the lens to the camera main body or the camera itself may not even have a mechanism for transferring state information about the image shake correcting operation. In addition, a system-level change in the interchangeable lens-type imaging apparatus cannot deal with an interchangeable lens which has already been used by a user, resulting in a significant disadvantage.
On the other hand, when in-plane (direction about the optical axis) rotational motion correction is further performed on an image obtained by optical image shake correction based on information about an attitude sensor mounted on the camera main body, such in-plane rotational motion correction may lead to oscillation of the translational motion correction remaining component for optical image shake correction. The negative effects become noticeable in the case of shooting while walking where the low-frequency components of shake are intentionally released and the motion of an object image is not completely stopped. In the mechanism or the like capable of dynamically switching the shut-off motion as disclosed in Japanese Patent No. 4692620, the negative effects become further noticeable when the cutoff frequency in the yaw direction largely differs from that in the pitch direction.